The present invention relates to an engine control device and an engine control method thereof.
In an engine control device of an automobile, a CPU of a microcomputer carries out various kinds of control processing on fuel injection by sensing detection signals representing a variety of operating states such as the engine speed of the automobile, the accelerator opening and the air pressure inside the intake pipe. In addition, the CPU also determines the start of electrical conduction in the ignition system and ignition timing in accordance with a crank angle signal in synchronization with the rotation of the engine by invoking an interrupt routine at predetermined time intervals. That is to say, in the course of processing carried out by the CPU, interrupt processing is triggered by an interrupt. The triggering frequency of the interrupt processing can be limited or the interrupt processing itself can even be inhibited. Inventions for limiting the triggering frequency of such interrupt processing are disclosed in the following patent applications.
In Japanese Patent Laid-open No. Hei 2-86943, there is disclosed an engine control device which comprises: a first computation means for computing control data of an engine by interrupt processing synchronized with the rotation of the engine; an upper level interrupt processing means for computing parameters such as an interrupt period and an interrupt execution time in processing at a level higher than the interrupt processing; a second computation means for computing a ratio of an execution time of the interrupt processing to an interrupt period of the first computation means; and an interrupt inhibiting means for inhibiting a next interrupt of the first computation means in case the ratio computed by the second computation means exceeds a predetermined value.
In Japanese Patent Laid-open No. Hei 6-249052, there is disclosed an engine control method whereby: while processing other than interrupt processing is being carried out a predetermined number of times, a computation means 2 counts the number of times the interrupt processing synchronized with the rotation of an engine is carried out; an execution frequency determining means 3 determines an execution frequency of the interrupt processing in accordance with the number of times counted by the computation means 2; and an inhibit means 4 inhibits computation of control data by a computation means 1 activated by an interrupt when the execution frequency determining means 3 determines to inhibit the computation of control data by the computation means 1.
In addition, in Japanese Patent Laid-open No. Hei 4-228854, there is disclosed an input inhibiting means. To put it in detail, in this application, there is disclosed an ignition device for an engine which comprises: an operating state detecting means for detecting the operating state of the engine; a pulse generating means for outputting a pulse signal at a predetermined crank angle of the engine; and a control circuit which provides a driving circuit with a command signal for executing various kinds of engine control including control of an ignition system after a predetermined period of time set in accordance with the operating state of the engine has lapsed since a point of time the pulse signal generated by the pulse generating means is input, wherein the engine ignition system is provided with the input inhibiting means for inhibiting the pulse signal from being input to the control circuit during a predetermined period of time following an issuance of an ignition command signal by the control circuit.
In Japanese Patent Laid-open No. Hei 4-228854, there is disclosed the input inhibiting means for inhibiting the pulse signal from being input to the control circuit during a predetermined period of time following an issuance of an ignition command signal by the control circuit. The invention disclosed in this application relates to timing advance control. Ignition noise is generated only during a period of about 50 microseconds following the issuance of an ignition signal by a control unit. Thus, by inhibiting a crank angle signal from being supplied to the control signal only during a predetermined period of typically 100 microseconds, erroneous detection of the crank angle signal caused by ignition noise can be avoided over the entire operating range, from a low engine speed to a high engine speed, without regard to what speed the engine is rotating at.
The two other inventions each relate to an interrupt inhibiting method to inhibit processing of an interrupt which occurs after processing with a higher priority has been started.
If unnecessary processing to handle an inadvertent interrupt that occurs due to noise or a software bug is carried out, the operability and the gas exhaust performance deteriorate. Thus, it is necessary to eliminate an inadvertent interrupt that has potential as a cause of deterioration of the operatability and the gas exhaust performance.
To put it in detail, the same routine may be activated again as an inadvertent interrupt caused by noise or a software bug. Execution of such unstable interrupt control will have adversely affected the operability and the gas exhaust performance.